Independent means for adjusting contact pressure and contact arm position



All@ 3, 1965 J. c. BRUMFIEL ETAL 3,198,924

INDEPENDENT MEANS FOR AD STING CONTACT PRESSURE AND CONTACT ARM POSITION Filed Feb. 2l, 1962 5 Sheets-Sheet 1 AUS'- 3, 1955 J. c. BRUMFlELD ETAL 3,198,924

INDEPENDENT MEANS FOR ADJUSTING CONTACT PRESSURE AND CONTACT ARM POSITION Filed Feb. 21, 1962 5 Sheets-Sheet 2 A ug. 3, 196s INDEPENDNT MEANS FOR ADJUSTING CONTACT PRESSURE AND CONTACT ARM POSITION Filed Feb. 21. '1962 .l vc. BRUMFIELD ETAL 3,198,924

5 Sheets-Sheet 5 FIG.3

All@ 3 1955 J. c. BRUMFIELD ETAL 3,198,924

INDEPENDENT MEANS FOR ADJUSTING CONTACT PRESSURE AND CONTACT ARM POSITION Filed Feb. 21, 1962 5 Sheets-Sheet 4 FIG.4

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UZ- 3, 1965 J. c. BRUMFIELD ETAI. 3,198,924

INDEPENDENT MEANS FOR ADJUSTING CONTACT PRESSURE AND CONTACT ARM POSITION 5 Sheets-Sheet -5 Filed Feb. 21, 1962 United States Patent O INDEPENDENT MEANS FOR ADJUSTING CON- TAC'I PRESSURE AND CONTACT ARM PO- SITION John C. Brumfield, Philadelphia, and Wilson W. Ponlton, Jr., Broomall, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania l Filed Feb. 21, 1962, Ser. No. 174,767

11 Claims. (Cl. 200-170) This invention relates to circuit breakers in general and more particularly to means for adjusting contact pressure without disturbing the spacing between the contacts in the open circuit position. l

In circuit breakers having quick make and quick break features the movable contact moves at a very high rate of speed into engagement with the stationary contact upon closing of the circuit breaker. Because of this it is necessary to provide means forvabsorbing the energy re,- leased by the closing mechanism in a very short travel of the movable contact.

In the circuit breaker art this has traditionally been accomplishedby mounting the stationary vcontact on a spring or providing a spring which is interposed between the movable contact and the closing mechanism. The springs must be of considerable strength tu maintain high pressure between the contacts when they are in engament so that good electrical contact is maintained in spite of magnetic blow-off forces which accompany current ow. Because of manufacturing tolerances it is necessary to adjust the contact pressure after the contact operating mechanism and stationary contacts are mounted to the circuit breaker base.

In recent years circuit breaker constructions have become so compact that finding room for locating the movable contact in the open position of the circuit breaker has presented a problem. That is, in order to achieve etlicient circuit interruption and prevent restriking of an arc there is a minimum distance required for contact separation in the open position of the circuit breaker.

Prior art means for adjusting contact pressure have comprised the shimming up of the stationary contact which is a tedious process and difficult to achieve in cramped quarters. In other prior art constructions contact pressure has been adjusted by lengthening or shortening'the contact pressure springs as required. But in each instance adjustment of the contact pressure springs resulted in changing the gap between the contacts in the open position of the circuit breaker.

The instant invention provides a construction for adjusting contact pressure without the necessity of changing the open circuit spacing between cooperating contacts'fVr This is accomplished by pivotally mounting the movable contact carrying arm to a carrier which forms part of the contact operating mechanism. The contact pressure spring is arranged to bias the contact arm into engagement with means carried by the carrier with this latter means establishing the open circuit position for the contacts. Loading of the spring in'order to achieve greater contact pressure or unloading of the spring to achieve reduced contact pressure will not alter the' spacing between contacts in the open position of the circuit breaker since, in all cases, the contact arm is biased into engagement with the carrier.

The construction of the instant inventionl is such that sequential opening and closing of contacts may readily be Because of this, the arcing contracts must be last to open and first to close when the circuit breaker is operated to the open and closed positions, respectively.

By utilizing the construction of the instant invention 5 this may readily be achieved.- First the open circuit gaps between the contacts of each pair cooperating contacts are set to achieve the desired sequential operation. Individual contact pressure springs are provided for each pair of cooperating contacts so that after adjustment of the gap settings. contact pressure adjustments may be made without affecting the gap setting so that sequential operation will be maintained with the required contact pressures.

Accordingly, a primary object of this invention is to provide a circuit breaker of a novel means for adjusting pressure between cooperating contacts.

Another object is to provide a contact pressure adjusting means which when adjusted will not affect the gap Y setting between contacts in the open position'of the circuit breaker.

Still another object is to provide a circuit breaker in which the movable contact carrying arm is pivoted to a carrier and the contact pressure spring is mounted to the carrier so as to bias the contact arm into engagement with a stop also carried by the carrier and positioned to establish the open circuit position for the movable contact.

A further object is to provide a circuit breaker which has a plurality of movable contacts for each phase thereof with means being provided to set the open circuit position of each contact and also means for establishing contact pressure with the latter means being adjustable without changing the open circuit positions for the contacts.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE l is a longitudinal cross-section taken through the center phase of a three-phase molded case circuit breaker constructed in accordance with the teachings of ltl the instant invention.

FIGURE 2 is a longitudinal cross-section of the contact operating mechanism.

The cross-sections of FIGURES 1 and 2 are taken through lines 1-1 and 2 2, respectively, ofv FIGURE 3 looking in the direction of the respective arrows.

FIGURE 3 is a plan view of the contact operating mechanism. j

FIGURE 4 is a cross-section taken through line 4-4 of FIGURE 2 looking in the direction of arrows 4 4.

FIGURE 5 is an exploded perspective of the movable contact mechanism of one of the outboard phases.

FIGURE 6 is a fragmentary cross-section showing an l alternate form of adjusting screw. l

r f Now referring to the figures: Circuit breaker 10 in- 5" cludes a housing comprising molded base 11 and a removable molded cover 12 joined together along line 13. Suitable barriers in base 11 and cover 12 divide the housing into three longitudinally extending compartments each housing the elements of an individual phase of circuit breaker l0.

The current carrying members of all three phases are identical so that for the sake of brevity only one of the sets of elements will be described. The current path ber tween line terminal strip 15 and load terminal strip 16 6" proceeds from stationary contacts 17 and 24 to movable contacts 18 and 25 carried by contact arms 19 and 26 through flexible braids 20 and strap 21 to bimetal heater each comprising a stationary contact 24 and a cooperating movable contact 25. Movable contacts 25 are each mounted to individual contact arms 26 each connected by an individual section of braid 20 to strap 21 while stationary contacts 24 are mounted to line terminal strip 15.

Circuit breaker 10 also includes an automatic tripping mechanism 28 and a toggle operating mechanism 29 each well known to the art. The details of mechanisms 28 and 29 form no part of this invention. For details reference is made to copcnding application Serial No. 108,8l2 filed May 9, 1961, in the name of E. Wortman entitled U- Shaped Cradle for Circuit Breaker and assigned to the assignee' of the instant invention.

Operating mechanism 29 is connected to the contacts of all three phases by means of'transverse insulating tie bar 30. U-shaped straps 31 connect all three contact carriers 32 to tie bar 30.

The center phase carrier 32 is connected at rods 36 to the lower end of the operating mechanism toggle 34, 35. The carrier 32 of the center phase is mounted at 33 to suitable bearingsstationarily mounted to base 11. As seen in FIGURE 5, three contact carrying arms 26, 19, 26 are pivotally mounted to a single carrier 32 by means of rod 36 which extends through aligned apertures 41 in the downturned arms of carrier 32.

As is well known to the art, upon opening of a circuit breaker, the cooperating main contacts must separate prior to separation of the cooperating arcing contacts and upon closing, the arcing contacts must engage prior to the engagement of the main contacts. Because of this, individual adjusting screws 43 are provided to establish the open circuit positiorfs of contacts 25, 18, 25 relative to stationary contacts 24, 17, 24.

Screws 43 extend upwardly through apertures 44 of contact arms 26, 19, 26 and elongated apertures 45 in the top surface of carrier 32. Nuts 46, having spring fingers, are threadably mounted to each screw 43 and when circuit breaker 10 is open rest against the upper surface of carrier 32.

Three tubes 47 extend upwardly from carrier 32 being fixedly mounted thereto and aligned with carrier apertures 48.` Tubes 47 provide housings for Contact pressure springs 49 whose lower ends are entered into guide recesses l50 of contact arms 26, 19, 26. The upper ends of springs 49 bear against the heads ofvadjusting screws v51 with these heads being disposed within tubes 47. The upperportion of each tube 47 is provided with a threaded aperture whose threads are mated with the threads of associated screw 51. Lock nuts 52 are mounted to screws 51 above the upper ends of tubes 47. The ends of screws 51 opposite the screw heads are provided with recesses to receive an Allen head wrench.

In order to reduce friction during adjustment screw 51 may be replaced by threaded rod 66a and disc 66b as shown in FIGURE 6. It is noted that disc 66h is separate from screw 66a and serves as a bearing plate therefor. S26

Springs 49 are compression members which bias the contact arms 26, 19, 26, clockwise with respect to FIG URE about rod 36. In the open position of the circuit breaker the clockwise movement of arms 26, 19, 26 is limited through the engagement of nuts 46 with the top surface of carrier 32.

To set circuit breaker for proper operation nuts 46 are positioned so that upon closing, within each phase, arcing contacts 17, 18 will engage prior to engagement of the two sets of main contacts 24, 25. With this setting, upon opening of circuit breaker 10, the sets of main contacts 24, 25 will disengage prior to the disengagement of arcing contacts 17,v 18.

After adjusting nuts 46, screws 51 are adjusted to either lengthen or shorten compression springs 49 so as to adjust contact pressure in the closed position of the breaker. Manipulation of screws 5l in no way affects 4 the positions of nuts 46 on screws 43 so that the open circuit positions of the contacts are unaffected.

Thus, this invention provides a simplied means for adjusting the open circuit contact positions as well as contact pressure. This construction is such that the contact pressure adjustment will in no way alter the previously made adjustment of open circuit contact position.

Although we have described preferred embodiments of our novel invention, many variations and modifica` tions will now be obvious to those skilled in the art, and we prefer therefore to be limited not by the specific disclosure herein but only by the appended claims.

We claim:

1. A circuit breaker comprising a pair of cooperating contacts; a contact arm carrying one of said contacts; operating means connectcd to said contact arm for moving said contact arm between a first and a second position wherein said contacts are disengaged and engaged, respectively; first means connected to said contact arm for establishing said first position; and adjustable second means connected to said contact arm for establishing pressure between said contacts when said arm is in said second position; said second means constructed and operatively positioned such that said first position remains fixed while said second means is adjusted; said operating means including a carrier having a pivot means to which said contact arm is mounted; said second means comprising spring means urging asid Contact arm about said pivot means toward the other of said contacts; said second means also comprising a readily accessible member for adjusting loading of said spring means; said spring means comprising a compression spring interposed between said carrier and said contact arm.

2The circuit breaker of claim l in which said first means comprises adjustable means extending between said contact arm and said carrier, said adjustable means providing a lost motion connection between said contact arm and said carrier.

3. A circuit breaker including a first and a second pair of cooperating contacts; a first contact arm carrying one Contact of said first pair and a second contact arm carrying one contact of said second pair; an operating means connected to said contact arms for moving each of said contact arms between a rst and a second position wherein said circuit breaker is open and closed, respectively; first means connected to said contact arm for establishing independent first positions for said contact arms; and adjustable second means connected to said contact arms for establishing independent contact pressures between the Contact of each pair when the Contact varms are in their second positions; said second means constructed and operatively positioned such that said first positions remain fixed while said second means is adjusted; said operating means including a single carrier having a pivot means to which both of said Contact arms are mounted; said second means comprising individual spring means for each of said pairs urging said contact arms about said pivot means toward the others of said cooperating contacts.

4. The circuit breaker of claim 3 in which the second means also comprises rapidly accessible members for individually adjusting loading of said spring means.

5. The circuit breaker of claim 4 in which each spring means comprises a compression spring interposed between said carrier and the respective contact arms.

6. The circuit breaker of claim 5 in which the first means comprises individual adjustable means for each of said pairs extending between the respective contact arms and the carriers, said adjustable means providing a lost motion connection between the respective Contact arm and said carrier.

7. A circuit breaker comprising a pair of cooperating contacts; a contact arm carrying one of said contacts; operating means connected to said contact arm for moving said contact arm hctwccn a first and a second position wherein said contacts are disengaged and engaged, respecbetween said contacts when said arm is in said second position; said second incaus constructed and operatively positioned such that said irst position remains fixed while said second means is adjusted; said operating means including a carrier having a pivot means to which said contact arm is mounted: said second means comprising spring means urging said contact arm about said pivot means toward the other of said contacts; said spring means positioned more remote from said pivot means than said first means. n

8. A circuit breaker comprising a pair of cooperating contacts; a contact arm carrying one of said contacts; operating means connected to said contact arm for moving said contact arm between a first and a second position wherein said contacts are disengaged and engaged, respectively; first means connected to said contact arm for establishing said first position; and adjustable second means connected to said Contact arm for establishing pressure between said contacts when said arm is in said secondvposition; said second means constructed and operatively positioned such that said rst position remains xed while said second means is adjusted; said operating means iricluding a carrier having a pivot means to which said contact arm is mounted; said second means comprising spring means urging said contact arm about said pivot means toward the other ol said contacts: said one of said contacts positioned at a first und of said contact arm and said pivot means positioned at thc other end of said contact arm; said spring means engaging said Contact arm in thc region of said lirst cud.

9. The circuit breaker of claim 8 in which said first means comprises adjustable means extending between said Contact arm and said carrier `said adjustable means providing a lost motion connection between said Contact arm and said carrier.

10. The circuit breaker of claim 9 in which the adjustable means comprises a member fixed to said contact arm and extending through a clearance opening in said carrier.

11. The circuit breaker of claim 10 in which the spring means is positioned more remote from said pivot means than said first means.

References Cited by the Examiner UNITED STATES PATENTS 1/60 Judd et al. 3/64 Cole et al.

German application, 1,059,541, June 18, 1959, 200 166 (2 shts. dwg., 2 pp. spec.). 

7. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS; A CONTACT ARM CARRYING ONE OF SAID CONTACTS; OPERATING MEANS CONNECTED TO SAID CONTACT ARM FOR MOVING SAID CONTACT ARM BETWEEN A FIRST AND A SECOND POSITION WHEREIN SAID CONTACTS ARE DISENGAGED AND ENGAGED, RESPECTIVELY; FIRST MEANS CONNECTED TO SAID CONTACT ARM FOR ESTABLISHING SAID FIRST POSITION; AND ADJUSTABLE SECOND MEANS CONNECTED TO SAID CONTACT ARM FOR ESTABLISHING PRESSURE BETWEEN SAID CONTACT WHEN SAID ARM IS IN SAID SECOND POSITION; SAID SECOND MEANS CONSTRUCTED AND OPERATIVELY POSITIONED SUCH THAT SAID FIRST POSITION REMAINS FIXED WHILE SAID SECOND MEANS IS ADJUSTED; SAID OPERATING MEANS INCLUDING A CARRIER HAVING A PIVOT MEANS TO WHICH SAID CONTACT ARM IS MOUNTED; SAID SECOND MEANS COMPRISING SPRING MEANS URGING SAID CONTACT ARM ABOUT SAID PIVOT MEANS TOWARD THE OTHER OF SAID CONTACTS; SAID SPRING MEANS POSITIONED MORE REMOTE FROM SAID PIVOT MEANS THAN SAID FIRST MEANS. 